EP1180521A1 - Method of producing allyltrichlorosilane - Google Patents

Abstract

In the production of allyltrichlorosilane (I) by dehydrochlorination of a chloropropyltrichlorosilane (II) or mixture of (II) isomers, the (II) component is treated in the gas phase in the presence of material(s) (III) of large surface area.

Description

The present invention relates to a new process for the production of Allyltrichlorosilane.

It is known that allyltrichlorosilane can be produced via the following routes:

A Grignard reaction can be used to convert allyl halides, preferably allyl bromide, magnesium metal and SiCl ₄ in ethers to allyl trichlorosilane (J. Am. Chem. Soc. (1951), 73 , page 2599; EP 0 879 822 A2; EP 0 798 302 A1). This method requires great care, especially with regard to the use of dry solvents and working under inert gas conditions, and is therefore only suitable for smaller laboratory batches. In addition, the process is very complex, gives low yields and the disposal of by-products is very expensive.

The reaction of allyl chloride with hexachlorodisilane to allyltrichlorosilane and SiCl ₄ requires either high temperatures in the gas phase (Zh. Obshch. Khim. (1966), 66 , pages 1484 to 1487) or the use of catalysts. For this purpose, in particular transition metals and transition metal salts, but also amines, are used as cocatalysts (J. Organomet. Chem. (1982), 225, pages 331 to 341; DE-OS 2 260 282; US 4,059,607). Hexachlorodisilane is one of many reaction products in the direct synthesis of organochlorosilanes and has to be isolated in a complex and cost-intensive manner or can be obtained in the traditional way by reductive coupling of SiCl ₄ with alkali metals. This fact and the rather high price of allyl chloride make this route for the production of allyltrichlorosilane very expensive.

Furthermore, SiCl ₄ and allyl chloride can be converted to allyltrichlorosilane in the presence of a special nickel catalyst, which is formed from nickelocene or nickel chloride and hexamethylphosphoramide (HMPA) (Tetrahedron Letters (1980), 21 , pages 1857 to 1860; FR 2 458 553) , This reaction requires stoichiometric amounts of disilane, which are split into the corresponding chlorosilanes, thereby reducing the catalyst and thus acting as acceptors of the two chlorine atoms released from allyl chloride and SiCl ₄ . This process is also complex and not very economical.

Trichlorosilane can be reacted in the presence of catalytic amounts of metal salts, for example CuCl, and stoichiometric amounts of tertiary amines as auxiliary bases with allyl chloride to form allyltrichlorosilane and the respective amine hydrochloride (J. Organomet. Chem. (1975), 96 , C1-C3; DD 289 766; JP 56 008 040). Although in this case all starting materials are easily accessible and the yields which can be achieved are satisfactory, the inevitable by-product accumulation and its separation and the almost impossible separation of by-product and catalyst make the process of industrial production of allyltrichlorosilane uninteresting.

In addition, allyltrichlorosilane can be obtained via the so-called direct synthesis from the reaction of silicon with allyl chloride in the presence of hydrogen chloride (HCl) at high temperatures (Organometallics (1993), 12 , pages 4887 to 4891; US 5,338,876). Copper is used as the catalyst. A similar reaction is known for the production of methylchlorosilanes for the production of silicone and can only be operated economically on a large scale, since a mixture of differently alkylated and chlorinated products is always produced.In contrast to direct synthesis with methyl chloride, the reaction with allyl chloride is accompanied by additional side reactions , Due to the fact that multiple allylated silanes are undesirable, this process is unsuitable for the production of allyltrichlorosilane.

It is also known to dehydrochlorinate chloropropyltrichlorosilanes, individually or as a mixture of isomers, in the presence of ferrosilicon or other metal powders such as iron or copper. However, gas phase dehydrochlorination at 400 to 450 ° C. in the presence of these solids only leads to yields of about 3 to 5% allyltrichlorosilane (Chem. Ber. (1959), 92 , pages 1012 to 1018). Higher yields of allyltrichlorosilane can be achieved in the liquid phase at the boiling point or below the boiling point of chloropropyltrichlorosilane in the presence of ferrosilicon and copper powder. However, this process has the disadvantage that very long reaction times (approx. 100 mmol / h) are necessary and, in addition to allyltrichlorosilane, the product also contains the undesired isomer propenyltrichlorosilane in part - up to the main amount (Chem. Ber. (1959), 92 , Pages 1012 to 1018; DE-OS 1 056 609).

It is also known that alkyl groups are different Dehydrogenation reactions can be converted into the corresponding olefins.

In the manufacture of 3-chloropropyltrichlorosilane, which is used as the starting material for Production of most organofunctional silanes is required in large quantities result from an undesirable side reaction, large amounts of n-propyltrichlorosilane (PTS) (see, inter alia, EP 0 519 181 A1).

This side reaction also consumes what is now a scarce resource Trichlorosilane.

Allyltrichlorosilane can be an interesting alternative to chloropropyltrichlorosilane for that Production of a variety of functional silanes. By adding more suitable ones Substrates to the terminal double bond can e.g. B. aminopropyl or Mercaptopropyl-functional silanes u. a. produce. In addition, allyl silanes, such as z. B. trialkoxyallylsilane, which is produced via alcoholysis from allyltrichlorosilane even interesting functional silanes, for example for Networking of thermoplastic materials.

So far, however, there have only been complex or very difficult ones Afflicted process for the production of allyltrichlorosilane, which has led to the fact that Allyltrichlorosilane because of its very high price not for the purposes mentioned in is used to a greater extent.

It was therefore the task of a further, as economical as possible process for Developing production of allytrichlorosilane. A special concern of the The present invention was to use PTS as the starting material component.

The object is achieved according to the information in the Claims resolved.

Surprisingly, it was found that allylchlorosilane can be used in simple and can produce economically if you can PTS in the gas phase at the same time in the presence of chlorine and at least one surface-rich material treated or if you first use PTS in the liquid or gas phase with chlorine implemented and then the resulting product mixture in the gas phase in Treated in the presence of at least one surface-rich material or if to 3-chloropropyltrichlorosilane (3-CI-PTS) in the gas phase in the presence of treated at least one surface-rich material. So got The crude product is generally worked up by distillation. Suitably one obtains Allyltrichlorosilane with a purity of 95 to 99.5% by weight, the Yield, based on the reactant component, in an advantageous manner, since particularly economical, is 60 to 80%. Unconverted components can come back in the process can be traced.

The present process also has the advantage over all others above mentioned methods for the production of allyltrichlorosilane the following advantages:

In the present process, no expensive raw materials, such as allyl chloride, Trichlorosilane or Disilane, but said waste PTS and that inexpensive chlorine used.

In addition to HCI and small amounts of chloro- and organochlorosilanes no difficult to separate or costly to dispose of By-products formed.

The present process is technically simple with standard equipment realize and only requires additional use in continuous operation of heating energy.

The catalysts to be used in the present process, i. H. Surface materials, especially activated carbon, are usually inexpensive, available in large quantities on the market and do not require any special Preparation.

In the present process, the preferred use of high-surface area activated carbon advantageously allyltrichlorosilane yields of up to 80% with regard to the implemented PTS or 3-CI-PTS, d. H. the respective Educt component, achieve.

The present invention therefore relates to a method for producing Allyltrichlorosilane by dehydrochlorination of a chloropropyltrichlorosilane or one Isomer mixture of chloropropyltrichlorosilanes, which is characterized in that that the chloropropyltrichlorosilane component in the presence of at least one surface-rich material treated in the gas phase.

The chloropropyltrichlorosilane component can be 3-chloropropyltrichlorosilane or 2-chloropropyltrichlorosilane or an isomer mixture of 3-chloropropyltrichlorosilane, 2-chloropropyltrichlorosilane and 1-chloropropyltrichlorosilane or any 2-component mixture use the substances mentioned.

i) n-Propyltrichlorsilan in einem ersten Schritt mit Chlor umsetzt und das resultierende Produktgemisch in einem zweiten Schritt in Gegenwart von mindestens einem oberflächenreichen Material behandelt
oder

(ii) n-Propyltrichlorsilan gleichzeitig in Gegenwart von Chlor und mindestens einem oberflächenreichen Material in der Gasphase behandelt
oder

(iii) 3-Chlorpropyltrichlorsilan in Gegenwart von mindestens einem oberflächenreichen Material in der Gasphase behandelt.

The process according to the invention for the preparation of allyltrichlorosilane is preferably carried out in such a way that

i) reacting n-propyltrichlorosilane with chlorine in a first step and treating the resulting product mixture in a second step in the presence of at least one surface-rich material
or

(ii) n-Propyltrichlorosilane treated simultaneously in the presence of chlorine and at least one surface-rich material in the gas phase
or

(iii) 3-chloropropyltrichlorosilane treated in the presence of at least one surface-rich material in the gas phase.

The implementation according to (i) first step of the process according to the invention is carried out preferably in a liquid phase reactor in the liquid phase at a Temperature in the range of 70 to 200 ° C and a pressure of 0.2 to 8 bar abs., particularly preferably at a temperature in the range from 100 to 150 ° C. and a pressure of 0.7 to 5 bar abs. and most preferably one Temperature in the range of 110 to 140 ° C and a pressure of 0.9 to 1.1 bar abs. by.

The reaction according to (i) first step can also be carried out in the gas phase a temperature in the range of 130 to 500 ° C and a pressure of 0.5 to 1.5 bar abs., Preferably at a temperature in the range from 200 to 400 ° C. and a pressure of 0.8 to 1.2 bar abs., particularly preferably at a temperature in the Carry out a range of 250 to 350 ° C and a pressure of 0.9 to 1.1 bar abs.

Suitably, in procedures (i) and (ii) of the process according to the invention, n-propyltrichlorosilane and chlorine (Cl ₂ ) are used in a molar ratio of 1 to 1/2 to 1 to 1/6, a 2- to 6- times, especially a 4 times, excess of PTS is preferred.

The reaction product obtained is preferably carried out according to (i) second step at a temperature in the range of 350 to 600 ° C and a pressure of 0.5 to 2 bar abs., Preferably at a temperature in the range from 400 to 500 ° C and a pressure of 0.8 to 1.5 bar abs., particularly preferably at a temperature in Range from 420 to 480 ° C and a pressure of 0.9 to 1.1 bar abs., Treated.

The treatment according to the invention can also be carried out in accordance with the Procedure (ii) at a temperature in the range of 130 to 600 ° C and one Pressure from 0.5 to 2 bar abs., Preferably at a temperature in the range from 200 to 400 ° C and a pressure of 0.8 to 1.5 bar abs., Particularly preferably at a Temperature in the range of 250 to 350 ° C and a pressure of 0.9 to 1.1 bar abs.

Furthermore, according to the invention, the treatment of procedure (iii) can be carried out as for variant (i) carry out the second step by using the 3-chloropropyltrichlorosilane feeds the reactor and in the presence of a surface-rich material in the Gas phase, preferably at a temperature in the range of 130 to 600 ° C and at a pressure of 0.5 to 2 bar abs., particularly preferably at a temperature in the range of 200 to 500 ° C and a pressure of 0.8 to 1.5 barabs., whole particularly preferably at a temperature in the range from 250 to 450 ° C. and a pressure of 0.9 to 1.1 bar abs., treated.

The process according to the invention is preferably carried out, in particular according to (i) second step or according to (ii) or according to (iii), in a tube reactor, tube bundle reactor, Fixed bed reactor, fluid bed reactor or fluidized bed reactor.

In the process according to the invention, a surface-rich material with an internal surface area (BET) of 500 to 2,000 m ² / g, preferably 600 to 1,600 m ² / g, particularly preferably 700 to 1,400 m ² / g, is suitably used. Activated carbon, zeolites or silica are preferably used as the surface-rich material, very particularly preferably activated carbon with surfaces of 1 1,300 m ² / g.

Furthermore, in the present process, an inert gas, for example N ₂ , Ar or H ₂ , can be added to the gaseous reaction or product mixture, in particular according to (i) second step or according to (ii) or according to (iii).

To carry out the method according to the invention, in particular according to (i) second step or according to (ii) or according to (iii), the reactor is preferably with a Gas velocity from 0.1 cm / s to 10 m / s, particularly preferably from 1 cm / s to 2 m / s, very particularly preferably from 5 cm / s to 1 m / s, flows through. Here is the average residence time of the gas in the reactor is preferably 1 second to 20 Seconds, particularly preferably 1 to 5 seconds.

Both the present method according to (i) and the procedure according to (ii) or (iii) is preferably operated continuously.

With regard to process variants (i) and (ii), the process according to the invention can be thought of as an oxidizing dehydrogenation of PTS to allyltrichlorosilane with chlorine as the oxidizing agent in the presence of high-surface area materials in the gas phase, so that two partial reactions can be formulated:

According to the invention, the two partial reactions according to (i) can be separated one after the other or according to (ii) quasi as a "one-pot reaction" together in one for it carry out a suitable reactor.

In the procedure according to (i), you can after the first sub-step (Chlorination) separate the resulting isomer mixture and the Compounds 1-chloropropylsilane, 2-chloropropylsilane and / or 3-chloropropylsilane to the second step (dehydrochlorination). When splitting can higher chlorination products may also be separated off. Especially It is surprising, however, that in the present process this is done by Chlorination resulting isomer mixture also in a particularly economical manner directly to the dehydrochlorination or the procedure according to Procedure (ii) can operate "as a one-pot reaction" and allyl trichloride receives unexpectedly high selectivities and good yields.

• Verfahrensweise (i) erster Schritt: Die Umsetzung von PTS mit Chlor erfolgt bevorzugt bei einer Temperatur von 100 bis 123 °C, besonders vorzugsweise beim Siedepunkt von PTS. Man kann die Umsetzung aber auch in Gegenwart von Licht, UV- sowie IR-Licht, und/oder in Gegenwart eines Chlorierungskatalysators, wie Y-Zeolithe, durchführen. Die Trichlorsilylgruppe von Organochlorsilanen ist gegenüber der Chlorierung inert, - so wird in der Regel kein SiCl₄ abgespalten. Die Umsetzung von PTS mit Chlor erfolgt vorzugsweise in flüssiger Phase am Siedepunkt des PTS. Geeigneterweise wird das Chlorgas vorher getrocknet und fein verteilt gasförmig durch die PTS-enthaltende Reaktionsmischung geleitet. Dabei kann das Reaktionsgemisch PTS und Lösemittel, wie Tetrachlorkohlenstoff, Hexachlorethan und andere, gegenüber Chlorierung inerte Lösemittel, enthalten. Für die Umsetzung kann man einen gängigen Chlorierungsreaktor aus Glas, Edelstahl, Emaile, etc. verwenden. Das als Nebenprodukt entstehende HCI kann beispielsweise über einen Rückflusskühler aus dem System entfernt werden. Die Chlorierung wird zweckmäßigerweise bei hohem Chlorunterschuss durchgeführt, um die Bildung von Dichloriden statistisch zu vermeiden. Chlorierungen gemäß (i) erstem Schritt können zweckmäßiger Weise so betrieben, dass ständig ein Teil der Chlorierungsmischung, die einen hohen Überschuss an PTS enthält destillativ in Edukt und Produkt aufgetrennt wird und das Edukt PTS in den Reaktionsraum zurückgeführt wird. Geeigneterweise ist somit eine kontinuierliche Fahrweise gegeben und es kann die Bildung von unerwünschten Dichlorpropyltrichlorsilanen weitestgehend unterdrückt werden. PTS, die drei möglichen Isomere 1-Chlorpropyltrichlorsilan, 2-Chlorpropyltrichlorsilan und 3-Chlorpropyltrichlorsilan, die beispielsweise in einem molaren Verhältnis 1:4:4 entstehen können, sowie die in geringem Maße gebildeten höher chlorierten Produkte lassen sich destillativ trennen.
• Verfahrensweise (i) zweiter Schritt: Der Dehydrochlorierungsschritt wird in der Regel an hochoberflächigen Stoffen als Katalysator durchgeführt. Die Behandlung erfolgt vorzugsweise in der Gasphase bei 350 bis 600 °C, bevorzugt bei 400 bis 500 °C, besonders bevorzugt bei 420 bis 480 °C, und einer mittleren Verweilzeiten zwischen 1 und 20 s, besonders bevorzugt 2 bis 10 s. Beispielsweise geeignet ist ein mit dem Katalysator gefüllter Rohrreaktor aus einem inerten Material, wie Metall, Glas, Keramik, d. h. Materialien, die bei rund 500 °C unter den vorherrschenden Bedingungen weitgehend beständig sind. Als Edukte für (i) zweiter Schritt können sowohl die einzelnen Isomere von Chlorpropyltrichlorsilan, wie auch Gemische daraus verwendet werden. Weiterhin kann das Edukt andere unter diesen Bedingungen inerte Stoffe, wie SiCl₄, enthalten. Bevorzugt sind aber keine weiteren Stoffe enthalten, um die Auftrennung des Produktgemisches zu vereinfachen. Die Edukte werden in der Regel entweder vor dem Eintritt in den Dehydrochlorierungsreaktor verdampft, oder innerhalb der ersten Zone innerhalb des Reaktors verdampft, die dafür nicht mit Katalysator gefüllt sein muss, sondern zweckmäßigerweise mit anderen Füllkörpern zur Wärmeübertragung gefüllt ist. Als Füllkörper eignen sich beispielsweise Metalleinsätze,Glaskugeln, Raschig-Ringe. Nach Austritt aus dem Reaktor wird das gasförmige Reaktionsgemisch in der Regel kondensiert und so vom gebildeten Chlorwasserstoff abgetrennt. Das flüssige Produktgemisch kann je nach Umsetzungsrate noch große Mengen nicht umgesetztes Chlorpropyltrichlorsilan enthalten, welches beispielsweise destillativ vom Produkt getrennt und geeigneterweise zur weiteren Umsetzung wieder verwendet wird.Weitere Nebenprodukte können insbesondere SiCl₄, Propen, Methyltrichlorsilan und Vinyltrichlorsilan sein. Verringert man beispielsweise die Verweilzeit, geht in der Regel der Umsatz zurück. Will man den Umsatz erhöhen, kann man die Verweilzeit erhöhen, allerdings kann dabei die Ausbeute an Allyltrichlorsilan zugunsten von Zersetzungsreaktionen sinken, z. B. können Methyltrichlorsilan, Vinyltrichlorsilan usw. entstehen. Variiert man bei gegebener Verweilzeit beispielsweise die Temperatur, kann man ein anderes Phänomen beobachten: Bei geringeren Temperaturen (ca. 300 bis 350 °C) findet bevorzugt eine andere Reaktion statt: die Zersetzung von Chlorpropyltrichlorsilan zu SiCl₄ und Propen. Bei höheren Temperaturen (ab ca. 500 °C) können zunehmend Zersetzungsreaktionen des intermediär gebildeten Allytrichlorsilans auftreten. Ebenso kann man hinsichtlich des Isomerenverhältnises Allyl-/Propenyltrichlorsilan beobachten.
  

In general, the method according to the invention can be carried out as follows:

• Procedure (i) first step: The reaction of PTS with chlorine is preferably carried out at a temperature of 100 to 123 ° C, particularly preferably at the boiling point of PTS. However, the reaction can also be carried out in the presence of light, UV and IR light and / or in the presence of a chlorination catalyst, such as Y zeolites. The trichlorosilyl group of organochlorosilanes is inert to chlorination, so no SiCl _{4 is} usually split off. The reaction of PTS with chlorine is preferably carried out in the liquid phase at the boiling point of the PTS. The chlorine gas is suitably dried beforehand and passed through the PTS-containing reaction mixture in finely divided gaseous form. The reaction mixture can contain PTS and solvents such as carbon tetrachloride, hexachloroethane and other solvents which are inert to chlorination. A common chlorination reactor made of glass, stainless steel, enamel, etc. can be used for the implementation. The HCI produced as a by-product can be removed from the system, for example, using a reflux cooler. The chlorination is expediently carried out when the chlorine deficit is high in order to statistically avoid the formation of dichlorides. Chlorinations according to (i) first step can expediently be carried out in such a way that part of the chlorination mixture which contains a large excess of PTS is continuously separated by distillation into starting material and product and the starting material PTS is returned to the reaction space. A continuous mode of operation is thus suitably given and the formation of undesired dichloropropyltrichlorosilanes can be largely suppressed. PTS, the three possible isomers 1-chloropropyltrichlorosilane, 2-chloropropyltrichlorosilane and 3-chloropropyltrichlorosilane, which can be formed in a molar ratio of 1: 4: 4, for example, as well as the slightly more highly chlorinated products formed can be separated by distillation.
• Procedure (i) second step: The dehydrochlorination step is usually carried out on high-surface materials as a catalyst. The treatment is preferably carried out in the gas phase at 350 to 600 ° C, preferably at 400 to 500 ° C, particularly preferably at 420 to 480 ° C, and an average residence time between 1 and 20 s, particularly preferably 2 to 10 s. For example, a tube reactor made of an inert material, such as metal, glass, ceramic, ie materials which are largely stable at around 500 ° C. under the prevailing conditions, is suitable with the catalyst. Both the individual isomers of chloropropyltrichlorosilane and mixtures thereof can be used as starting materials for (i) second step. Furthermore, the educt can contain other substances which are inert under these conditions, such as SiCl ₄ . However, no further substances are preferably present in order to simplify the separation of the product mixture. The starting materials are usually either evaporated before entering the dehydrochlorination reactor, or evaporated within the first zone within the reactor, which does not have to be filled with catalyst for this purpose, but is advantageously filled with other packing elements for heat transfer. Metal inserts, glass balls, Raschig rings, for example, are suitable as packing elements. After leaving the reactor, the gaseous reaction mixture is generally condensed and thus separated from the hydrogen chloride formed. The liquid product mixture can, depending on the reaction rate is still large quantities contain unreacted chloropropyltrichlorosilane, which, for example separated by distillation from the product and suitably re-used for further reaction wird.Weitere by-products can in particular SiCl _4, propene, methyltrichlorosilane and vinyltrichlorosilane be. If, for example, the retention time is reduced, sales usually decrease. If you want to increase sales, you can increase the residence time, but the yield of allyltrichlorosilane can decrease in favor of decomposition reactions, e.g. B. methyltrichlorosilane, vinyltrichlorosilane, etc. can arise. If, for example, the temperature is varied for a given residence time, a different phenomenon can be observed: At lower temperatures (approx. 300 to 350 ° C) another reaction preferably takes place: the decomposition of chloropropyltrichlorosilane to SiCl ₄ and propene. At higher temperatures (from approx. 500 ° C), decomposition reactions of the intermediate allytrichlorosilane can increasingly occur. One can also observe allyl / propenyltrichlorosilane with regard to the isomer ratio.
  

Illustration 1:

• Verfahrensweise (ii) Hierbei wird PTS und Chlor in Gegenwart eines Oberflächenreichen Materials in der Gasphase behandelt bzw. umgesetzt. Dafür kann einem beheizten Reaktor zunächst PTS, flüssig oder gasförmig, zugeführt und geeigneterweise im erstem Abschnitt des Reaktionsrohres Chlor zudosiert werden. Geeigneterweise betreibt man den Reaktor mit einem Temperaturgradienten im Bereich von 150 bis 600 °C. Dabei sind im Einlassbereich bis hin zur Reaktormitte 150 bis 500 °C, insbesondere 250 bis 450 °C, und zum Reaktorauslass hin 350 bis 600 °C, insbesondere 420 bis 480 °C, bevorzugt. Die Dosierung des Chlors erfolgt zweckmäßigerweise über mehrere hintereinander angeordnete Dosierstellen, sodass stets ein Chlorunterschuss zur Vermeidung der Dichloridbildung verwendet werden kann. Im weiter Verlauf des Reaktor kann dieser mit dem oberflächenreichen Material bestückt oder ausgekleidet sein. Das den Reaktor verlassende Rohprodukt wird in der Regel destillativ aufgearbeitet, wobei das im Überschuss eingesetzte Chlor sowie nicht umgesetztes PTS als Edukte zurückgeführt werden können.
  

Figure 1 shows the diagram of a preferred embodiment of a continuously operated system according to the invention according to procedure (i) (separate chlorination and dehydrochlorination).

• Procedure (ii) PTS and chlorine are treated or reacted in the gas phase in the presence of a surface-rich material. For this purpose, PTS, liquid or gaseous, can first be fed to a heated reactor and chlorine can be metered in suitably in the first section of the reaction tube. The reactor is suitably operated with a temperature gradient in the range from 150 to 600.degree. 150 to 500 ° C., in particular 250 to 450 ° C., and 350 to 600 ° C., in particular 420 to 480 ° C., are preferred in the inlet region up to the middle of the reactor. The chlorine is expediently metered via a plurality of metering points arranged one behind the other, so that a chlorine deficit can always be used to avoid the formation of dichloride. As the reactor continues, it can be equipped or lined with the surface-rich material. The crude product leaving the reactor is generally worked up by distillation, and the excess chlorine and unreacted PTS can be recycled as starting materials.
  

Figure 2:

• Verfahrensweise (iii) Im Allgemeinen wird als Edukt 3-Chlorpropyltrichlorsilan (3-CI-PTS) dem Reaktor zugeführt und hier in Gegenwart eines oberflächenreichen Materials in der Gasphase behandelt. Hierfür gilt im Grundsatz auch das bereits für die Verfahrensweisen (i) zweiter Schritt sowie (ii) Offenbarte. So liefert die erfindungsgemäße Dehydrochlorierung von 3-CI-PTS in einfacher und wirtschaftlicher Weise Allyltrichlorsilan-Ausbeuten bis zu 80 % bezüglich 3-CI-PTS. Außerdem kann in vorteilhafter Weise ein Isomerenverhältnis der Dehydrochlorierungsprodukte Allyltrichlorsilan und Propenyltrichlorsilan (H₃C-CH=CH-SiCl₃) von 35 : 1 erreicht werden, was einer Allyltrichlorsilanreinheit von ≥ 97 % entspricht.
  

Figure 2 shows the diagram of a preferred embodiment of a continuously operated system according to the invention according to procedure (ii) ("one-pot reaction").

• Procedure (iii) In general, 3-chloropropyltrichlorosilane (3-CI-PTS) is fed to the reactor as the starting material and is treated here in the gas phase in the presence of a surface-rich material. In principle, what has already been disclosed for procedures (i) second step and (ii) also applies to this. The dehydrochlorination of 3-CI-PTS according to the invention thus provides allyltrichlorosilane yields of up to 80% with respect to 3-CI-PTS in a simple and economical manner. In addition, an isomer ratio of the dehydrochlorination products allyltrichlorosilane and propenyltrichlorosilane (H ₃ C-CH = CH-SiCl ₃ ) of 35: 1 can advantageously be achieved, which corresponds to an allyltrichlorosilane purity of ≥ 97%.
  

Figure 3:

Figure 3 shows the schematic of a preferred embodiment of a Plant to be operated continuously according to procedure (iii).

The present invention is illustrated by the following examples:

example 1 Chlorination of PTS

in a 1 l four-necked flask with gas inlet tube, dropping funnel, reflux condenser, The patio heater and internal thermometer are initially charged with 500 g of PTS and the Reflux heated. Via an outlet at the bottom of the piston, a Dosing pump removed approx. 400 ml of liquid per hour and poured into a Distillation column given, which is able to the chlorinated products as a bottom separate cleanly. The top product of this column thus contains almost pure PTS, which flows back into the reaction flask. Having a stable here Cycle is formed with the dosage of 40 g of chlorine gas per hour started, which was previously by passing through conc. Dried sulfuric acid becomes. At the same time, 100g PTS are dosed per hour via the dropping funnel, so that overall there is continuous operation. At the bottom of the column become approx. 120 g per hour after setting a stationary operating state chlorinated product deducted. This driving style results in arithmetically chlorination a molar fourfold excess of PTS, so that the formation of Dichlorides is pushed back. According to the GC, the product formed has the following Composition (% by weight): 9.95% 1-chloropropyltrichlorosilane, 42.11% 2-chloropropyltrichlorosilane, 45.48% 3-chloropropyltrichlorosilane and together 2.73% dichlorinated products (6 isomers in total).

Examples 2 to 9 dehydrohalogenation

A total of 211 g of high-surface area activated carbon (Picatal D7, 4 x 8 mesh, BET surface area 1,300 m ² / g) are placed in a metal tube 62 cm long and 34 mm inside diameter over a length of approx. 50 cm. This results in an empty tube volume of 162 ml in this area. The remaining volume of the tube is filled with Raschig rings. This tube is heated to 350 to 500 ° C (for the exact value see Table 1) using a tube furnace. On the side of the Raschig rings, chloropropyltrichlorosilane (3-chloropropyltrichlorosilane or isomer mixture from Example 1) is now metered in, in addition to a uniform stream of inert gas (nitrogen, dry) (for the metered amount see Table 1). This now evaporates in the zone of the Raschig rings, is passed through the activated carbon zone and reacts there. At the outlet of the tube, the gaseous reaction mixture is condensed and collected using a reflux condenser. The exhaust gases (HCl, possibly propene) leave the system via an intensive cooler (-20 ° C). The condensates collected there are combined with the others and analyzed (GC).

Claims (16)

Process for the preparation of allyltrichlorosilane by dehydrochlorination of a chloropropyltrichlorosilane or an isomer mixture of chloropropyltrichlorosilanes,
characterized in that the chloropropyltrichlorosilane component is treated in the presence of at least one surface-rich material in the gas phase. Method according to claim 1,
characterized in that one i) reacting n-propyltrichlorosilane with chlorine in a first step and treating the resulting product mixture in a second step in the presence of at least one surface-rich material
or (ii) n-Propyltrichlorosilane treated simultaneously in the presence of chlorine and at least one surface-rich material in the gas phase
or (iii) 3-chloropropyltrichlorosilane treated in the presence of a surface-rich material in the gas phase. The method of claim 1 or 2,
characterized in that a surface-rich material with an inner surface area (BET) of 500 to 2,000 m ² / g is used. Method according to one of claims 1 to 3,
characterized in that activated carbon, zeolites or silicas are used as the surface-rich material. Method according to one of claims 1 to 4,
characterized in that the treatment in the gas phase at a temperature in the range from 120 to 600 ° C and a pressure in the range from 0.3 to 2 bar abs. performs. Method according to one of claims 2 to 5,
characterized in that the reaction according to (i) first step in a liquid phase reactor in the liquid phase at a temperature in the range from 70 to 200 ° C and a pressure of 0.2 to 8 bar abs. performs. Method according to one of claims 2 to 5,
characterized in that the reaction according to (i) first step in the gas phase at a temperature in the range from 130 to 500 ° C and a pressure of 0.5 to 1.5 bar abs. performs. Method according to one of claims 2 to 7,
characterized in that the treatment according to (i) second step at a temperature in the range from 350 to 600 ° C and a pressure of 0.5 to 2 bar abs. performs. Method according to one of claims 2 to 5,
characterized in that the treatment according to (ii) at a temperature in the range from 130 to 600 ° C and a pressure of 0.5 to 2 bar abs. performs. Method according to one of claims 2 to 9,
characterized in that n-propyltrichlorosilane and chlorine are used in a molar ratio of 1 to 1/2 to 1 to 1/6. Method according to one of claims 2 to 5,
characterized in that the treatment according to (iii) at a temperature in the range from 130 to 600 ° C and a pressure of 0.5 to 2 bar abs. performs. Method according to one of claims 8 to 11,
characterized in that one carries out the process according to (i) second step or according to (ii) or according to (iii) in a tube reactor, tube bundle reactor, fixed bed reactor, fluidized bed reactor or fluidized bed reactor. Method according to one of claims 1 to 12,
characterized in that an inert gas is added to the gaseous reaction or product mixture. Method according to one of claims 1 to 13,
characterized in that the reactor is flowed through at a gas velocity of 0.1 cm / s to 10 m / s to carry out the process. The method of claim 14
characterized in that the average residence time of the gas in the reactor is 1 second to 20 seconds. Method according to one of claims 1 to 15,
characterized in that the process is operated continuously.